Back-up plate for double-sided buffing pad

ABSTRACT

A back-up plate is provided for a reversible double-sided rotary buffing pad. The back-up plate is attached directly to the output shaft of the power buffer and the buffing pad is attached to the back-up plate and, when attached, circumferentially spaced fingers on the outer edge of the back-up plate bear on the unused buffing face and prevent excess flexing and premature fracture and failure of the backing disk on the interior of the pad that supports the oppositely disposed buffing faces.

BACKGROUND OF THE INVENTION

[0001] The present invention pertains to apparatus for buffing and polishing painted surfaces and, more particularly, to a supporting back-up plate for a double-sided rotary buffing pad.

[0002] The finishing of painted or clear coated surfaces of automobiles and the like includes the use of a variety of buffing, polishing and finishing tools, finishing compounds and apparatus, including both manually operated devices and power driven buffing machines. Rotary buffing pads used with power buffers include tufted wool pads, polymeric foam pads, and pads of other types and constructions of buffing and finishing materials.

[0003] A power buffer typically has a driven output shaft or spindle to which a rotary buffing pad is attached, usually by a threaded connection. Because a rotary buffing pad has a buffing surface that is inherently soft and somewhat flexible, such pads are typically mounted on or attached to some sort of backing plate against which the rear face of the pad opposite the working surface rests and is supported. The backing plate may be relatively rigid or may provide substantial flexibility, depending on the nature of the buffing pad itself and/or the type of finishing work being done.

[0004] Rotary buffing pads having a reversible double-sided construction are also known in the art. Such pads are made of both tufted wool and polymeric foam and typically include identical opposite finishing faces such that when one face becomes excessively worn or dirty, the pad is detached from the drive spindle of the power buffer, reversed and reattached to present a fresh buffing face. One such reversible pad is shown in U.S. Pat. No. 5,461,750. In a typical construction of a double-sided pad, the opposite facing finishing pads are mounted back-to-back on an annular interior backing disk which is secured to a center hub that carries the threaded connection for attachment to the buffing machine spindle. To provide the necessary strength and yet provide needed flexibility, the backing disk typically has a heavier section where it is attached to the hub, which section thins in a radially outward direction so that the peripheral edge of the backing disk is quite thin and flexible. In use, the flexible backing disk allows the operator to move easily over contoured surfaces and into more confining areas and, in general, provides a necessary flexibility that skilled workers desire. Unfortunately, the strain and fatigue to which a solid plastic backing disk is subjected through high speed rotation and cyclical bending pressure from the operator often results in premature cracking, fracture and ultimate failure of the backing disk. The very nature of a double-sided pad simply does not lend it to the use of backing plates of the type used with single faced rotary buffing pads. It would, therefore, be desirable and useful to provide some means of supporting a double-sided rotary buffing pad to eliminate or reduce the problem of fracture of the backing disk and yet retain some of the necessary flexibility of the working face.

SUMMARY OF THE INVENTION

[0005] In accordance with the present invention, a separate back-up plate for a double-sided buffing pad is interposed between the power buffer drive spindle and the double-sided pad. The back-up plate provides intermittent supporting contact through the use of circumferentially spaced peripheral fingers in contact with the non-working face of the pad.

[0006] A back-up plate is provided for a reversible double-sided buffing pad of the type having a center hub adapted for attachment to the drive shaft of a power buffer. The back-up plate comprises a plate body that is mounted on a center plate hub which hub includes an upper fastener attachable to the drive shaft of the power buffer and a lower fastener attachable to the center hub of the pad. The plate body has a generally circular shape when viewed in plan, including a center body portion that extends radially outward and generally perpendicular to the plate hub axis. The radial outer peripheral edge of the body portion terminates of the plurality of circumferentially spaced, downturned fingers. The free distal ends of the fingers engage the non-working face of the pad when the pad is attached to the plate body via the lower fastener.

[0007] The plate hub preferably comprises a generally tubular sleeve including a threaded ID portion forming the upper fastener and an axially extending threaded stud forming the lower fastener. The plate body is preferably rotatably mounted on the plate hub to facilitate attachment of the pad thereto. In a preferred embodiment, the plate hub is made of metal and the plate body is made of a thermoplastic material. Preferably, the plate body has a cylindrical axial through bore and the OD of the plate hub is received in the through bore with a slip fit to provide relative rotation therebetween.

[0008] In the preferred embodiment, the outer peripheral edge of the center body portion of the back-up plate is rounded to blend smoothly into the fingers and to define a downwardly facing continuous edge comprising convergent curved edge portions defining the fingers, the distal ends of which fingers define flat contact edge surfaces. Each finger includes an integral reinforcing rib that extends from the distal ends thereof into the body portion and terminates adjacent the plate hub.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a side elevation of the back-up plate of the subject invention shown operatively mounted between a buffing pad and the drive shaft of a power buffer.

[0010]FIG. 2 is a vertical section through the back-up plate taken on line 2-2 of FIG. 4

[0011]FIG. 3 is an enlarged exploded view of the center hub portion of the back-up plate shown in FIGS. 2 and 4.

[0012]FIG. 4 is a bottom plan view of the back-up plate of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] As best seen in FIG. 1, the back-up plate 10 of the present invention is particularly useful with a double-sided rotary buffing pad 11. The back-up plate 10 is interposed between the pad 11 and the drive spindle or drive shaft 12 of a power buffer. As will be described, the back-up plate 10 is attached to the drive-shaft 12 in the same manner as the double-sided pad 11 would be attached to the drive shaft were the back-up plate not used. However, the interposition of the back-up plate provides an important support function, particularly when using a double-sided pad, to prevent damage to the pad and increase its useful operating life.

[0014] The double-sided pad 11 is of a conventional construction, including opposite buffing faces 13 of tufted wool construction. However, working faces of other know buffing material such as pulmeric foam, are also known and used. The tufted wool buffing face is attached to a backing layer 14 of cloth or the like and the backing layer is then secured with a suitable adhesive to a backing disk 15 which provides the main support for the buffing faces. The backing disk 15 is preferably molded of a suitable plastic material in a manner to capture and be rigidly secured to a center hub 16. The hub 16 is provided with a threaded ID 17 by which, in prior art use, provided direct threaded attachment to the end of the drive shaft 12. The interior backing disk 15, as shown in FIG. 1, includes a heavier and thicker central section near the hub 16 which tapers radially outwardly to a substantially thinner outer section 20. The thinner outer section provides flexibility to the pad which is desirable in buffing operations, but is also the characteristic that leads to cracking and failure as a result of overload or fatigue.

[0015] The back-up plate 10 of the present invention provides a backing support for the double-sided pad 11 that permits the pad to flex sufficiently in operation, but which prevents overstressing which would result in premature cracking and failure of the backing disk 15. The back-up plate includes a main plate body 21 which has a generally circular shape when viewed in plan, including a center body portion 22 that extends radially outward from and generally perpendicular to the central axis. The center body portion 22 blends smoothly into a curved outer edge portion 23 to define a sort of dome-like overall shape. However, the curved outer edge portion 23 is cut out or scalloped to define an outer peripheral edge 24 that includes a plurality of circumferentially spaced downturned fingers 25. The distal or free ends of the fingers are flattened to provide pad-contacting edge surfaces 26. Thus, as shown in FIGS. 1 and 2, the plate body 21 has a downwardly facing continuous edge defined by semicircular cut out edge portions 27, adjacent ones of which converge downwardly to define the fingers 25 and terminate at the edge surfaces 26.

[0016] The center of the plate body 21 is provided with a cylindrical axial through bore 28 by which the plate body is rotatably mounted on the center plate hub 30. Referring also to FIG. 3, the plate hub 30 is formed from a generally tubular metal sleeve 31 having a threaded bore 32. The sleeve 31 is sized to be received in the through bore 28 of the plate body 21 with a slip fit. The upper portion of the sleeve 31 is provided with an exterior annular flange 33 that provides a stop when the sleeve is inserted into the bore 28 in the plate body. A threaded stud 37 is threaded into the lower end of the threaded bore 32 of the tubular sleeve and secured in place with a flange nut 35. The flange nut 35 also secures the plate body 21 in its rotatable mounting on the tubular sleeve 31. The exposed face of the flange nut 35 is preferably provided with a shallow counterbore 36 to accommodate the upper edge of the pad center hub 16. The exposed lower end of the stud 37 is threaded into the ID 17 of the pad hub 16 to secure the back-up plate 10 the pad 11. As the stud 37 is threaded into the upper end of the pad hub 16, the edge of the hub is received and bottoms in the counterbore 36. As the stud 37 enters the pad hub 16, the edge surfaces 26 of the back-up plate fingers 25 move axially into contact with and extend into the tufted wool fibers on the upper buffing face 13 of the pad. However, the rotatable mounting of the back-up plate body 21 on the plate hub 30 allows the plate body to rotate freely during the thread-up process, thereby avoiding interfering drag of the fingers 25 over the tufted wool.

[0017] The back-up plate fingers 25 are dimensioned and positioned such that the end faces 26 bear on or be closely spaced from the outer peripheral edge of the interior backing disk 15. In this manner, the fingers prevent excess deflection and bending of the backing disk, while allowing some necessary flexing because of the inherent compressibility of the tufted wool buffing face layer. Furthermore, the buffing pad 11 has a greater diameter than the back-up plate 10 such that the common outer peripheral edge of the buffing faces 13 is completely unobstructed for use by the operator in buffing and finishing the surface of recesses, corners and the like. For a pad having a standard nominal diameter of 7½″ (190 mm) the back-up plate 10 will have a diameter of about 5″ (about 125 mm).

[0018] Referring to FIG. 4, the underside of the back-up plate 21 is provided with reinforcing ribs 38 which extend in a generally curved arc from the distal ends of the fingers 25, along the central body portion 22, and terminate at a center boss 40 that defines the through bore 28.

[0019] Because the back-up plate hub 30 attaches to the buffer drive shaft 12 and via the threaded bore 32 in essentially the same manner in which the center hub 16 of the double-sided pad would attach directly to the drive shaft and, in turn, lower end of the plate hub attaches directly to the buffing pad (via the threaded stud 37), no special fasteners or adapters are needed. Thus, the back-up plate 10 of the present invention is easy to attach and its use protects a double-sided pad from damage and premature failure, while allowing uninhibited operation of the buffing process. 

I claim:
 1. A back-up plate for a reversible double-sided rotary buffing pad, said pad having a center hub adapted for attachment to the drive shaft of a power buffer, said back-up plate comprising: a plate body mounted on a center plate hub, said plate hub including an upper fastener attachable to the drive shaft and a lower fastener attachable to the center hub of the pad; and said plate body having a generally circular shape when viewed in plan, including a center body portion extending radially outward from and generally perpendicular to the plate hub axis, the radial outer peripheral edge of the body portion terminating in a plurality of circumferentially spaced downturned fingers, the distal ends of which engage one side of the pad when attached to the plate body.
 2. The apparatus in claim 1 wherein the plate hub comprises a generally tubular sleeve, said upper fasteners comprising a threaded ID in said sleeve, and said lower fasteners comprising a threaded stud.
 3. The apparatus in claim 1 wherein said plate body in rotatably mounted on said plate hub.
 4. The apparatus in claim 3 wherein said plate hub is metal and said plate body is a thermoplastic.
 5. The apparatus in claim 3 wherein said plate body includes a cylindrical axial through bore, and the OD of the plate hub is received in the through bore with a slip fit.
 6. The apparatus in claim 1 wherein the outer peripheral edge of said center body portion is rounded to define a downwardly facing continuous edge comprising convergent curved edge portion defining fingers, the distal ends of which define flat contact edge surfaces.
 7. The apparatus in claim 6 including an integral reinforcing rib extending from the distal and of each finger into the body portion and terminating adjacent the plate hub. 